It IS tight in there, and it does sometimes TAKE a lot of pressure, but...If I were guessing, I'd say that there is enough junk in the end of the trunions, between the lube passageway and the bearing caps that it may not be completely distributing grease. The only way to confirm this would be to take the joint a part and inspect it. If you go to that length, on 135k joints, I'd suggest getting a pair of Spicer brands and put them in. It is a good idea to mark the driveshaft and the pinion yoke to put it back in the same position.